Circuit interrupter



y 1- v R. LUDWIG ETAL 43, 39

CIRCUIT INTERRUPTER Filed Jan. 4, 1939 I5 Sheets-Sheet 1 Fig 1.

0 15 O O Q WITNESSES: INVENTORS Lean R.Ludwiga11d May 20, 194.1- R. LUDWIG ETAL CIRCUIT INTERRUPTER Filed Jan. 4, 1939 3 Sheets-Sheet 2 w I 7 m 4 Q m 5 5 l .c 5 e @w M IIlll IIII IIII III L| llllh lII Ifr IIIIIIIIIIIIIIIIIIIIL I I I I I l I l I l l I i Insulatiob II llllll lll lllrll Nag/7277c Wafer 4 m H m n E r O VdO T mH m R W B Z M 1 May 20, 1941. L. R. LUDWIG ETAL CIRCUIT INTERRUPTER Fig: 4.

WITNESSES:

Mayne/7c Maferl'aL Patented May 20, 1941 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTER Application January 4, 1939, Serial No. 249,210

13 Claims.

This invention relates to circuit interrupters and more particularly to are extinguishing devices for circuit breakers of the air break type.

In the application of L. R. Ludwig, Serial No. 216,884, filed July 1, 1938, and assigned to the assignee of this application, there is shown and described an arc extinguishing device of the foregoing type in which are extinction is accomplished by magnetically blowing an arc laterally into relatively narrow slots disposed in plates of insulating material. The plates of insulating material are of such width and spaced a distance apart that no material looping or bowing of the arc takes place between the plates at the closed ends of the slots, thereby causing the arc to be held in a relatively stationary position, and while being so held to be subjected to a blast of relatively cool unionized gas produced by the same magnetic action which initially caused arc movement to the end of the slots.

The instant invention has for its object the provision of improvements in an arc extinguishing structure of the type described in the aforesaid application, whereby more efficient and effective arc movement and gas blasts are obtained.

Another object of our invention is the provision of an arc extinguishing structure of the aforesaid type in which the magnetic field producing means is disposed with respect to the plates of insulating material in a manner to materially increase the voltage rating 01' the device.

A more specific object of the invention is the provision of a magnetic field producing structure for are extinguishing devices of the air break type, whereby arc extinction is facilitated during the interruption of alternating-current circuits by maintaining the are under the influence of an effective magnetic field during the time the arc current passes through zero in its cyclic wave.

A further object of the invention resides in the provision of improvements in an arc extinguishing device of the aforesaid type directed to decreasing the rate of deterioration of the arc extinguishing plates by the action of the arc thereon.

Additional objects and advantages will appear hereinafter in the specific description of the structural embodiments of our invention as shown in the accompanying drawings, in which:

Figure 1 is a side elevation view or the circuit interrupter of our invention showing a portion of the arc extinguishing device broken away to reveal the position of the are drawing contacts with respect to the arc extinguishing plates;

Fig. 2 is an enlarged side levation view, partially in section, of the arc extinguishing device of our invention;

Fig. 3 is an end elevation view, partially in section, of the are extinguishing device of Fig. 2;

Fig. 4 is an end elevation view of a modified form of plate structure which may be used in our arc extinguishing device;

Fig. 5 is a fragmentary sectional view of the plate structure shown in Fig. 4, taken along the line V V thereof;

Fig. 6 is an end elevation view of another form of plate structure which may be used in our arc extinguishing device; and

Fig. 7 is a fragmentary sectional view of the plate structure shown in Fig. 6, taken along the line VIIVII thereof.

In Figure l of the drawings, the reference numeral 9 designates a panel upon which a pair of stationary main contacts I I and iii are mounted in spaced relation. The main contacts II and I3 are bridged by a contact member I5 operatively carried by a movable operating arm l'l pivoted at its lower end at l9 to a supporting frame 2| also mounted upon the panel 9. A stationary arcing contact 23 is connected to the stationary main contact II and cooperates with a movable arcing contact 25 carried by the contact arm 21, which is also associated with the operating arm H. The operating arm I! is associated with an operating mechanism generally indicated at 29 for actuating the bridging contact l5 and the arcing contact 25 to the open circuit position. Inasmuch as the specific contact arrangement and the operating mechanism therefor is not specifically claimed in the instant application, further details relating to the construction thereof may be obtained by referring to the application of M. E. Horn, Serial No. 216,708, filed June 30, 1938, now Patent No. 2,214,471 dated September 10, 1940, and also assigned to the assignee of the instant application.

When the contacts 23 and 25 separate under load, an are established therebetween is adapted to be extinguished by an arc extinguishing device ll shown in detail in Figs. 2 and 3. The are extinguishing device ll comprises a back support plate 33 and a front support plate 35, each of insulating material, between which are disposed a plurality of plates 31 of insulating material. The plates 31 are provided with four apertures 39 to facilitate the assembly thereof upon an equal number of insulating tubular rods II. The plates 31 are spaced from each other by-insulating spacing members 43 disposed along opposite side edges of the plates. Bolt 45 passing through the two lower tubular rods 4| and also through the front and back support plates 33 and 35 clamp the plate assembly in the assembled position. The two upper tubular rods 4| of insulating material provide through passages to the panel 9 for bolts (not shown) for securing the are extinguishing device to the panel 9. The insulating spacing members 43 are held in alignment along their inner edges by the tubular rods 4|, and along their outer edges by cover plates 41 secured to the front and back support plates 33 and 35 by screws 49, as more clearly shown in Fig. 3.

Each of the plates of insulating material 31 is provided with a V-shaped slot extending inwardly from the lower end thereof, and preferably has a configuration as more clearly shown in Fig. 3. Disposed above and in abutting relation with each plate 37 is a plate 53 of magnetic material such as iron, which is maintained between the spacing strips 43, and is preferably of the same thickness'as the plates 3! so as to form a continuation thereof. In order to prevent displacement of the plates 53 of magnetic material upwardly, a pair of longitudinally extending bar members 55 secured along the upper edge of each side plate 41 are provided which register with rectangular detents 51 formed in the upper corners of the plates 53.

The operation of the device is as follows: Upon the separation of arcing contacts 23 and 25 within the enlarged lower portions of the slots 5|, an arc is established which immediately moves upwardly into the narrower portions of the slots 5| as a result of the inherent magnetic reaction combined with the normal thermal effect produced by the are. In addition to the inherent tendency for movement of the are upwardly, the plates of magnetic material 53 are positioned only adjacent the restricted end of the slots 5| so as to have set up therein a magnetic reaction due to the arc current to create a magnetic field which increases in intensity as the arc is moved towards the plates 53 and further assists in the movement of the arc. This magnetic reaction is sufficient to force the are into the restricted narrow slot-like portions wherein arc extinction takes place.

In accordance with the theory fully set forth in the aforesaid application of L. R. Ludwig, Serial No. 216,884, the are upon reaching the closed ends of the slots 5| is, due to the particular spacing of the plates 31 and the thickness of these plates, as well as the strength of the magnetic field acting thereon, prevented from looping or bowing a substantial distance between the plates. While the arc is thus maintained at the apex of the slots 5|, the spaces between the plates determined by the spacing members 43 permits ionized gas particles to freely escape upwardly. Movement of these ionized particles from out of the arc stream is accelerated by the action of the magnetic field. Unionized gas particles are, therefore, continually moved into and through the arc stream which must become ionized if the arc is to be maintained. However, this action of moving the relatively unionized gas particles into the arc stream materially raises the arc voltage. Thus the magnetic field creates a gas blast through the are which in a very short interval of time raises the arc voltage to such a degree that the arc can no longer be maintained and are extinction takes place.

More effective are extinction is obtained when the plates are constructed of refractory materials or'materials which evolve substantially no gas when acted upon by an arc, such as asbestos-board, quartz, soapstone or titanium oxide. Cold molded compositions, as, for instance, a product known as artificial porcelain comprising 30% talc, 2% feldspar, and 68% clay, are also suitable. In general, all materials which are refractory in nature and have the requisite mechanical strength are suitable for this purpose.

It has also been found that more efficient arc extinction is obtained when the plates 31 of -insulating material are from to inch in thickness and spaced from each other from to inch. It is also of importance that the slots 5| in each of the plates 31 have a given configuration. For example, the slot that varies in width from inch at its apex to A; inch at a point two inches removed therefrom has substantially the proper taper at its upper or narrower end. The lower portion of the slot, however, may increase in width more rapidly, and as long as the sides have a smooth contour and are of sufficient width to permit the moving contact 25 to pass therethrough, no difficulty is experienced in obtaining the requisite arc movement.

We have also found that it is desirable to extend the narrow portion of the slots 5| to within approximately inch of the magnetic plates 53. Although this particular distance is preferred, it is not critical, in that satisfactory operation has also been obtained by shortening the distance between the ends of the slots 5| and the plates 53 ofmagnetic material even though the corrosive effect of the hot arc gases upon the metal plates 53 was more pronounced. Although positioning of the plates 53 a. greater distance from the apex of the slots 5| decreases the corroding effect upon the plates 53, the magnetic reaction set up in the plates for moving the are into the slots becomes less effective.

By using spacing members 43 of insulating material between adjacent plates 31 it has been made possible to utilize a plate 53 of magnetic material across the upper end of each plate 5| of insulating material, thereby greatly increasing the number of plates of magnetic material and consequently materially strengthening the magnetic field for are movement and for the creation of a gas blast. The use of magnetic plates, as shown and described in the aforesaid application of L. R. Ludwig, for spacing the plates 3'! of insulating material from each other would require the alternate use of plates of insulating material extending between the cross plates of magnetic material, in order to secure the requisite overall insulation of the arc extinguishing device. The are extinguishing device shown in Figs 2 and 3 is capable of interrupting arcs of at least 250 volts per inch arc length on direct current, and at least 350 volts per inch arc length on alternating current. More specifically an arc extinguishing device as herein shown having an effective arc length of 6 inches has successfully interrupted 20,000 amperes at 2500 volts alternating current.

In order to increase the interrupting voltage so as to adapt the device for operation in a higher voltage circuit, it is desirable to provide a plate structure as shown in Figs. 4 and 5. As shown in these figures, an occasional plate 31 of the foregoing structure has been omitted and a longer plate 59 substituted therefor. The plates 59 extend beyond the upper end of the plates 53 of magnetic material and, therefore,

The eifect of staggering the slots in the plates,

as shown in Fig. 4, is tocause a more rapid rise in the arc voltage, which in turn causes an are which has moved to the end of the slot to momentarily be extinguished and restrike at a lower point along the narrow portion of the slot. thus an oscillating effect is obtained which materially decreases the burning effect of the are along the narrow portion of the slot.

We have also discovered that improved operation may be obtained by the provision of a plate structure, as more particularly shown in Figs. 6 and 'I. In this instance, the plates 50 are the same as previously described, whereas the shorter plates designated as 66 have a trapezoidal sectioai 66 removed from each upper corner, as more clearly shown in Fig. 6. This permits the use of a U-shaped magnetic plate 61 to be employed in which the opposed legs extend into the cutout sections 66 of the plates 66. The leg portions of the plates 61, however, extend only a short distance along the sides of slots 6i and 63 and flare outwardly so as to produce a magnetic field which increases in intensity as the arc approaches the closed ends of the slots. The transverse or yoke portions on the magnetic plates 61 are covered with a sheath of conducting material such as copper or the like. The purpose of the sheath 6! is two-fold. First, it protects the magnetic plates 61 from the direct attack by the hot arc gases passing through the venting spaces between the plates and, therefore, permits positioning the plates of magnetic material 61 closer to the apex of the slots, with the resulting increase in the magnetic action for bringing about are extinction. Secondly, the copper sheath 69 forms a short-circuited connection about the yoke of each plate 61 so as to bring about a phase shift in the fiux produced in the plate by the arc current, so that during the interruption of alternating current a substantial magnetic field will be maintained at current zero. This is of particular importance in bringing about are extinction at the most propitious time in the current wave; that is, when the current is passing through the zero region of the wave.

From the foregoing description it will be apparent that the modifications in plate structures shown in Figs. 4 and 5, and 6 and "I, either with aligned or staggered slot constructions, may be substituted for the particular plate structure shown in Figs. 2 and 3. It is also to be understood that the use of a staggered slot arrangement as shown in Figs. 4 and 6 in the particular plate structure shown in Figs. 2 and 3 is within the teachings of the present invention.

Although we have shown and described a specific circuit interrupter and an arc extinguishing device or devices therefor, it is to be understoodthatthesameisforthepurposeofillustration, and that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

We claim as our invention:

1. In a circuit interrupter, an arc extinguishing device comprising a plurality of plates of insulating material, means spacing said plates irom each other, each of said plates having a tapered notch extending inwardly from one end thereof, said notches forming a groove in which an arc is adapted to play, means for establishing an are along said groove, and a plate of magnetic material for each of a plurality of said plates of insulating material disposed in abutting relation edgewise across the end thereof adjacent the closed end of said notch, said plates of magnetic material setting up a magnetic reaction for moving the arc towards the closed end of said notches and causing a blast of gas to pass laterally through the arc, said plates of magnetic material extending only acrossthe ends of said plate; of insulating material at the closed ends of said notches so that said magnetic reaction set up by said magnetic plates increased in intensity with movement of the arc towards the closed ends of said notches.

2. In a circuit interrupter, an arc extinguishing device comprising a plurality of plates of insulating material, each of said plates having a slot extending inwardly from one end to substantially the other end thereof, said plates being arranged in spaced relation with respect to each other and with the open ends of said slots in alignment and with the closed ends of said slots in staggered relation, means for establishing an are within the aligned open ends of said slots, and a plate of magnetic material for each of a plurality of said plates of insulating material disposed in abutting relation edgewise across the end thereof adjacent the closed end of said slot, said plates of magnetic material setting up a magnetic reaction for moving the arc towards the closed ends of said slots and causing a blast of gas to pas laterally through the arc, said plates of magnetic material extending only across the ends of said plates of insulating material at the closed ends of said slots so that said magnetic reaction set up by said magnetic plates increases in intensity with movement of the arc towards the closed ends of said slots.

3. In a circuit interrupter, an arc-extinguishing device comprising a plurality of plates of insulating material, means of insulating material disposed between each of said plates along the opposed side edges thereof, each of said plates having a tapered slot extending inwardly from one end to substantially the other end thereof, means for establishing an arc in the open ends of said slots, and a plurality of plates of magnetic material disposed in alignment with said plates of insulating material and only across the ends thereof adjacent the closed end of said slots for moving the arc laterally towards the closed ends of said slots, said plates of magnetic material setting up a magnetic field across said slots for moving the arc, which field increases in intensity in accordance with movement of the arc towards the closed ends of said slots, the thickness of said plates of insulating material, the spacing thereof and the dimensions of said slots being so proportioned that arcs of at least 250 volts per inch of arc length are extinguished by said device.

4. In a circuit interrupter, an arc extinguishing device comprising a plurality of plates of insulating material, means spacing said plates from each other, each of said plates having a slot extending inwardly from one end thereof, said slots having an entrance portion which decreases in width rapidly from the open ends thereof for a substantial distance along the longitudinal axis of the slots and a narrower remaining portion which decreases in width at a slower rate, means for establishing an arc in said entrance portion of said slots, and means of magnetic material for biasing said are laterally towards the closed ends of said slots, said means of magnetic material being so arranged with respect to the ends of said slots that the biasing force produced by said means of magnetic material increases in magnitude in accordance with movement of said are towards the closed ends of said slots, said plates being arranged with the entrance portions of said slots in alignment and with the remaining narrow portions of said slots in staggered relation to cause said arc to oscillate longitudinally of said narrow slot portions. i"

5. In a circuit interrupter, an arc extinguishing device comprising a stack of plates of insulating material arranged in spaced relation to provide venting spaces between adjacent plates, each of said plates having a'tapered arc receiving slot of uniform length extending inwardly from one end thereof, means for establishing an arc in said slots, said slots in alternate plates having at least a portion adjacent their closed ends displaced laterally with respect toeach other to provide a zig-zag path for said are, certain of said plates being of greater length than the remaining plates, and a plate of the stack of plates and having a length at least equal to the combined length of said shorter plates and said plates of magnetic material to prevent the formation of an arc across said plates of magnetic material.

6. In a circuit breaker for interrupting an alternating current circuit, an arc extinguishing device comprising a plurality of plates of insulating material, a slot in each of said plates extending inwardly from one end thereof, means for establishing an arc in said slots, a plurality of plates of magnetic material disposed across the ends of said plates of insulating material adjacent the closed ends of said slots, said plates of magnetic material being so arranged with respect to said slots that in the presence of said are a magnetic field is set up for moving the arc towards the closed ends of said slots which field increases in intensity as the arc is moved toward the closed ends of said slots, and means associated with said plates of magnetic material for shifting the phase relation between said magnetic field and the arc current to cause a substantial field to persist at current zero.

'7. In a circuit breaker for interrupting an alternating current circuit, an arc extinguishing device comprising a plurality of plates of insulating material, a slot in each of said plates extending inwardly from one end thereof, means for establishing an arc in said slots, U shaped plates of magnetic material having opposed leg portions joined by a transverse yoke and disposed to form extensions of at least a plurality of said plates of insulating material and arranged with said leg portions on opposite sides of a slot in a plate of insulating material, said plates of magnetic material in the presence of said are causing a magnetic field for moving the arc toward the closed ends of said slots, and a shortcircuited conductor about the yoke of each plate of magnetic material for causing said magnetic field to be maintained through current zero.

8. In a circuit breaker for interrupting an alternating current circuit, an arc extinguishing device comprising a plurality of plates of insulating material, a slot in each of said plates extending inwardly from one end thereof, means for establishing an arc in said slots, means spacing said plates from each other to provide venting passages therebetween, U shaped plates of magnetic material having opposed leg portions joined by a transverse yoke and disposed to form extensions of at least a plurality of said plates of insulating material and arranged with said leg portions on opposite sides of a slot in a plate of insulating material, said plates of magnetic material in the presence of said arc causing a magnetic field for moving the arc toward the closed ends of said slots and a blast of gas laterally through said arc, and a short circuited sheath of copper about the yoke of each plate of magnetic material for causing said magnetic field to be maintained through current zero and for preventing the hot arc gases from impinging upon said yokes.

9, In a circuit interrupter of the air break type, an arc-extinguishing device comprising a plurality of spaced plates, each of said plates having a notch therein in which an arc is adapted to play, means for establishing an arc in said notches, means of magnetic material adjacent one end of said notches for establishing a magnetic field across said end of the notches for moving the arc toward said end, and said means of magnetic material extending no more than a small distance toward the other end of said notches.

10. In a circuit interrupter of the air break type, an arc-extinguishing device comprising means of insulating material having a notch therein in which an arc is adapted to play, said means of insulating material having vent passages extending therethrough from one end of said notch to the outside thereof, means for establishing an arc in said notch, means of magnetic material positioned at said end of the notch for moving the arc toward said end of the notch and for causing a flow of gas from said notch through the arc and out said vent passages, and said means of magnetic material being positioned only adjacent said end of the notch.

11. In a circuit interrupter, an arc extinguishing device comprising a plurality of spaced plates of non-gas forming insulating material, said plates having substantially aligned tapered slots extending inwardly from one of their ends, means laterally within said slots and into said constricted tips following decay of the instantaneous current below said predetermined magnitude. said magnetic means exerting a progressively greater force upon said are as it moves towards the closed ends of said slots.

'12. In a circuit interrupter, an arc extinguishing device comprising a stack of plates 0! insulating material, means spacing said plates a predetermined distance from each other to provide vent a through the stack, said plates having elongated tapered notches therein which terminate in a constricted tip decreasing progressively in width from no greater than V." at a point at least 2" from the closed end of the notches to no greater than 1'." at the closed end, means for establishing an arc within said notches, and plates of magnetic material disposed only adjacent to the closed ends ofsaid notches v to provide a magnetic held for moving said arc into said constricted tips which field increases in intensity as the arc moves towards the closed ends of said notches.

13. In a circuit interrupter, an arc extinguishing device comprising a stack of plates of insulating material, means spacing said plates a predetermined distance from each other to provide venting passages. said plates being substantially free from materials which give 0! gas when acted upon by an arc and having elongated tapered notches therein, saidtapered notches decreasing progressively in width from the open to the closed ends thereof and having a constricted portion of at least 2" in length adjacent the closed ends thereof of width to prevent entry therein of alternating current arcs of a predetermined instantaneous current magnitude, means for establishing an are within said notches, and means of magnetic material for moving the are into the constricted portion of said notches following decay of the instantaneous value of the arc current below said predetermined magnitude where it is cooled and extinguished, said means of magnetic material being positioned only adjacent the closed ends of said notches ior progressively exerting a greater force upon the are as it moves towards the closed ends of said notches.

LEON R. LUDWIG. MERL E. HORN. 

